Effects of a Mutual Promise

“...and so, we are glad to have them back.” Celestia finished her speech, creating much applause throughout the castle. Twilight’s castle was hosting a royal event for the second time, this one a celebration of finding her after nearly a hundred days of being missing. Not only that, Twilight was the first non-alicorn mare in a thousand years to be transformed by the island. Primarily it was a party for Tempest, the second partner of an alicorn in years. Marefriend, technically. It wasn't quite an engagement party, but it was at least a welcome back and congratulations party. The queens and their associated staff stood on the central stairway inside the castle, looking out over a moderately sized crowd.

"Well. Now that that's out of the way..." Tempest put her arm around her marefriend, "I think I’d prefer to retire to our chambers. Shall we, my darling?"

Twilight flushed, even after all this time. "T-Tempest--!"

Celestia looked at them and smiled. “Of course, you may leave. You’ve been through so much, you should be free to enjoy yourselves.” She winked at Luna, and the queen of the moon gave a smile.

Twilight blushed and nodded with a thumbs up. Tempest gave a toothy grin, then stealthily pulled them out of the group of advisers and staff surrounding the royals, and up the stairs to the sides. Twilight fought to keep up. She wore a brand new modest dress Rarity made for her. It was sleeveless but ran from her knees up to her neck, limiting her stride. Tempest wore a tight suit, barely big enough for her new frame.

The pair were no longer the mares they once were, physically at least. After spending time on a lost alicorn land known as Betrothal Island, their bodies had been radically transformed into new physiques. These were based on the alicorn’s powerful forms meant to control extreme magical energies. As they moved, Twilight had to avoid looking too closely at her marefriend’s rear. These forms had some… bonuses.

Tempest brushed past the guards on the stairway, with Twilight apologizing every other step. She led them up the stairs, around the corner, and into one of the castle’s side corridors. Twilight threw the door shut. The party atmosphere and sound were cut off by the doors.

Twilight threw her hands around her marefriend. She felt her good broad shoulders, her huge muscular body, as their lips met. Tempest held her midsection, appreciating the well-built torso of her beautiful lover. They made out immediately, trying to get themselves even closer than they already were.

They finally broke. Tempest’s eyes went to her side. “You’ve got good soundproofing in this place, I could see myself liking it,” she murmured.

“Maybe don’t get used to it?” Twilight said, half serious, “You said before, we don’t have to stay with this level of privilege…I can stand living with a little less…uh… extravagance.”

Tempest nuzzled her head. She knew her lover wasn’t one for all the pomp and circumstance of her position. “I’m not used to it, but I could see us getting it even if we find a better way to rule than just alicorns. I think even a… what were those ideas? Chairpony, the president? Even if we had those in charge, they might need a place like this.” Tempest grinned, “Especially with the hottest alicorn of the bunch.”

Tempest’s hand strayed down to feel up her lover’s ass. Twilight made an odd sound and stood on her tip-toes. They made out further, until finally, Twilight burst out, “Oh, sweet goddess, I can’t wait.”

She looked around and led them to a nearby bathroom, one of the public ones on the castle ground floor. Tempest kicked the door shut, locked it and jammed a trash can under the handle for good measure.

Entering the bathroom, she put Twilight on the sink. Tempest pulled off her suit jacket and hung it up, undid her bowtie, and with a spell, teleported off her pants. Twilight was struggling with the belt. Tempest simply grabbed the side of the dress and pulled it off, tearing it down to miniskirt length. "Deja vu..." Tempest breathed in her ear.

Twilight grabbed the front of her marefriend's button-down shirt and ripped it open, heedless of the buttons tinkling everywhere. She held her Tempest's breasts and squeezed them, spraying milk everywhere. Tempest groaned, "Oh, that's how you want to play it. She ripped open Twilight's dress and grabbed her much larger breasts, then tore open the front of the dress, opening it like a door and leaving Twilight naked. Tempest speared herself on her marefriend, "Your mistress is here."

She thrust into her. Over and over she sprayed her. "Give it all to me!" Twilight moaned.

"You asked for it...!" Tempest delivered and held her lover to her. She fired again and again, squirting like a cannon.

Twilight looked several months pregnant when she was done. They were both covered in sweat. Twilight rubbed her stomach, "Oooh..."

Tempest kept her member inside her, holding her to her chest. Tempest moaned out as Twilight took the opportunity to drink her milk. Tempest looked down at herself, at her altered body. She could barely see past her breasts. She was more attractive and muscular than she'd ever been. And she was embedded in the princess of friendship. "Can we go one day without having sex?"

Twilight shook her head, "Nope. Going a day with only one round of sex is a challenge as it is."

She stood up. Tempest was fully erect again and held out her arms. Twilight was impaled on her cock and held up by it. It only lasted a second, but Twilight orgasmed on the spot. She wrapped her arms and legs around her lover, relaxing against her embrace. They teleported back to their chambers in a flash. They locked the doors and settled in for a long night of passion.

They had other responsibilities and things to do, but it seemed they had their transformation magic under control.

Amid the party, a certain blue unicorn had snuck into Twilight’s private kitchen and opened the refrigerator. What she unleashed would not be contained for some time…